Field of the Invention
The present invention relates to a magnetic tape, a magnetic tape cartridge, and a magnetic recording and reproducing device.
Discussion of the Background
Magnetic recording media include tape-shaped media and disk-shaped media. Magnetic recording media in the form of tapes, that is, magnetic tapes, are primarily employed in storage applications such as data-backup tapes.
When recording a signal on or reproducing a signal from a magnetic tape, a magnetic tape cartridge housing the magnetic tape is normally loaded into a drive, and the magnetic tape is run within the drive, bringing the surface of the magnetic tape (surface of the magnetic layer) into contact with (causing it to slide over) a magnetic head. Hereinafter, the term “magnetic tape” will also be referred to simply as a “tape” and the term “magnetic head” will also be referred to simply as a “head”.
In the above recording and reproduction, since running in which the surface of the magnetic layer slides over the head is conducted repeatedly, a portion of the surface of the magnetic layer is shaved off or the like, generating foreign material that sometimes adheres to the head. When the magnetic tape is repeatedly run with foreign material adhering to the head in this manner, the foreign material alters the distance between the magnetic tape and the head, sometimes causing the output to fluctuate (which is referred to as “spacing loss”). Such spacing loss causes a drop in the electromagnetic characteristics with repeated running. As a countermeasure to this, abrasive has conventionally been incorporated into the magnetic layer to impart to the surface of the magnetic layer the function of removing foreign material adhering to the head (for example, see Japanese Unexamined Patent Publication (KOKAI) No. 2014-179149 or English language family member US2014/272474A1 and Japanese Unexamined Patent Publication (KOKAI) No. 2005-243162, which are expressly incorporated herein by reference in their entirety). The function of removing foreign material that has adhered to the head from the surface of the magnetic layer will be referred to as the “abrasiveness of the surface of the magnetic layer” or simply “abrasiveness” hereinafter.